Google once brashly believed that its engineers could invent a solution to the world's energy problems. These days, the company has a new strategy: finance less risky clean-energy projects where it can actually make an impact.

Last year, Google invested more than ever in renewable power, spending $880 million to underwrite conventional clean-energy projects such as solar panels on California rooftops. But that isn't the role the company envisioned for itself in 2007, when cofounder and current CEO Larry Page declared that it would get into energy research directly, intending to "rapidly" invent cheap ways to generate "renewable electricity at globally significant scale."

Google believed its creativity and innovation would make the difference. It created an in-house plan to wean the United States off fossil fuel in 22 years. It posted jobs for engineers who could speed up design of renewable-energy projects and put a team to work improving the heliostat, a mirrored device that focuses the sun's rays to make thermal energy.